Fuel cells typically comprise a set of individual cells each constituted by two electrodes (anode and cathode) separated by an electrolyte and assembled one against the other so as to form a stack. By feeding each electrode with an appropriate reagent, namely a fuel for one of the electrodes and an oxidizer for the other, an electrochemical reaction is obtained which enables a potential difference to be created between the electrodes, and thus enables electricity to be produced. The stack corresponds to the core of the fuel cell since it is within the stack that the electrochemical reaction takes place that enables electricity to be generated.
In order to feed each electrode with reagent and to collect the electricity produced, specific interface elements are used that are generally referred to as “bipolar plates”, which elements are disposed on either side of the individual cells.
Such bipolar plates are generally in the form of a single component adjacent to the anode or cathode support. They perform several functions associated with the chemical reaction respectively at the cathode and at the anode. These functions are as follows:                feeding the electrodes with reagent;        enabling each of the reagents to circulate in confinement;        collecting electrical current and providing electrical continuity through the stack;        collecting and removing the water produced together with any excess reagent; and        removing the heat energy dissipated by the reaction.        
Consequently, such elements are subjected to numerous constraints concerning selection of their component material(s) and their methods of manufacture. The elements must be made of a material which is simultaneously a good conductor of electricity and heat, which withstands attack from the medium (acidic or basic), and which is impermeable to the reacting gases. In addition, each element must include millimetric distribution channels on each of its faces in order to enable the reagent to be delivered uniformly to the electrodes and in order to manage removal of water together with any excess reagent.
The most common embodiments make use of graphite, and machining techniques are implemented using tools, such as etching, in order to form the reagent distribution channels. Such machining techniques are very expensive and difficult to reproduce identically for each part.
Another known technique consists in using thin-plate metal heat-exchanger technology, where the plates are shaped by stamping or thermocompression, for example. Nevertheless, making and assembling such parts is difficult since that assumes that leaktightness is guaranteed between the assembled elements, which makes large-scale industrial manufacture difficult to envisage.
Whatever the technique that is adopted, it is the interface element forming the bipolar plate that determines the size and the mass of the stack, and above all, to a very large extent, the cost of the structure, and thus the cost of the fuel cell.
Thus, in spite of their high energy efficiency, and in spite of being environmentally friendly in operation, fuel cells are present in very few apparatuses, and often only on an experimental basis. Industrial and commercial development of fuel cells is presently greatly restricted by certain difficulties that have not yet been overcome. At present, cost represents the main obstacle to large-scale production and competitive commercialization of fuel cells.